dman: WJaxson: The sensor size for me was important, from a low light ability point of view, and from an ability to create a narrow depth of field image, but I fully take on board your comments of the practical issues of nailing focus with such a narrow depth of field and the camera / subject movement. In practise most modern sensors are pretty good anyway, and without getting into the real picky specifics, they can all do a pretty good job nowadays .
Nailing focus vs modern sensors are two very different things... or maybe those two sentences are just accidentally in the same paragraph together and there is not meant to be any connection between them?
Sensor size was related to light gathering capabilities, and to the depth of field obtainable for a given lens.
Nailing focus was in relation to how practical to work with that narrow depth of in focus field actually is.
New sensors all being pretty good was with regards to light gathering abilities, amount of noise at higher ISO etc. In practise most modern cameras are all good with regards to their sensors ability.
Software though, yes video has a long way to go with it's implementation on a lot of devices. Many companies have all the bits, the hardware especially, but they drop the ball on some aspect with regards to video, be that codec, or stabilisation attempts as in the case of the Pentax, or a lack of audio level display etc etc.
My take on sensor size is related to a photographer want to emulate a full frame shot for portraits on my APS-C equipped bodies, not video specifically at all. It's a laugh still though that full HD is still only 2MP in size, so the higher the sensor resolution (not physical sensor size) the more the software has to do something to reject most of the information coming at it.
Sorry if the above wasn't particularly clear, I'm racing to pump out these replies when I get a moment. On the whole I agree with much of what you're saying and appreciate the comments. Good comments from all, thanks!